The present invention relates to an improved ball valve, specifically designed for domestic and industrial gas systems, according to the preamble of claim 1.
Ball valves in general, and in particular for domestic and industrial gas systems, can optionally comprise tampering indicating means, designed to clearly indicate a possible tampering of the valve manual operating elements, such as operating knobs, levers or the like, which will be hereinafter generically called xe2x80x9cdriving leverxe2x80x9d, and which are coupled to a screw element for rotatively driving a valve ball shutter, by geometrically engaging it, and being clamped on said screw element by a clamping threaded nut engaged on a free threaded end portion of the screw element.
The above mentioned a geometric fitting is usually performed by providing two parallel and opposite flat portions at the free threaded end of the screw element and a corresponding opening, having parallel sides coupled by portions of a circumference of a diameter corresponding to the screw outer diameter, through the lever, so as to engage the clamping nut on said threaded portions of the screw. In particular, after having assembled and locked the lever by the nut, between the inner circumference of said nut and said screw flat portions, two free chambers, closed at the bottom by the lever and freely communicating at the top thereof with the outside, will be formed.
For meeting machining accuracy requirements, the outer threaded end of the screw is moreover formed with a blind hole which, upon assembling, is left free.
Starting from the above disclosed prior art ball valve construction, two approaches for indicating a possible tampering have now been herein devised, the first of which provides to apply a colored paint drop or strip extending from a point of the nut side surface to the adjoining underlying driving lever, thereby a tamper of the lever, i.e. an unthreading of the nut, would cause an visually detectable breaking of the paint drop or strip.
However, in actual practice, such a visual detection of the paint drop or strip breakings is hindered both by the small surface of the paint drop or strip and by the fact that said breaking usually consists of a thin cross slit which, upon re-screwing the nut, would be not longer apparent.
The main drawback of this approach, however, is that, the tampering can be easily concealed by simply applying a further paint strip or drop on the broken slit.
The second approach, being adopted by the Applicant, provides to use a nut housing therein, at its outer end, a plastic material ring which, upon threading the nut on the screw, is self-threaded on the screw to be clearly seen from the outside. Thus, upon unthreading said nut, the plastic material ring, which is properly colored, disengages therefrom to clearly indicate its tampering.
The above mentioned approaches, moreover, can be hardly standardized by some Foreign State Authorities, for example based on the European standard En 331/1998 stating a lot of requirements on visually showing possible tamperings in ball valve.
Accordingly, the aim of the present invention is to provide a ball valve in which it would be very easy to visually show possible tamperings thereof.
The above mentioned aim is achieved, according to the invention, by a ball valve having the features of claim 1.
Further advantageous embodiments are disclosed in the dependent claims.
Claim 2 discloses a very simple embodiment of the invention, having a single anchoring cavity and providing an easily visually detectable anti-tampering seal, anchored in a reliable manner.
Claim 3 discloses a first modified embodiment including a double anchoring cavity.
Claim 4 discloses a triple anchoring chamber, providing a very reliable anchoring or clamping of the valve anti-tampering indicating means.
As disclosed in claim 5, the outer portion of the anti-tampering means or seal extends through the overall outer face of the clamping nut, thereby it can be clearly univocally seen.
This vision facility and clearness is further improved by the solution claimed in claim 6.
As disclosed in claim 7, the anchoring cavities provided herein have a small height thereby conventional or depressed clamping nuts can be used.
As disclosed in claim 8, a plastic material or a low melting metal or metal alloy, such as a lead, tin alloy, can be used as the injectable or molding material.
As disclosed in claim 9, it is possible to clearly visually detect a performed tampering.
Thus it should be apparent that the invention provides a lot of important advantages, such as a visually clear indication of a tampering. Moreover, upon tearing away, the anti-tampering seal cannot be reconstructed thereby providing a permanent tampering indication. While the herein proposed anchoring cavities can be suitably dimensioned and shaped appropriately depending on their molding material, it is advantageously possible to use the cavities already existing in prior ball valves, so as to use them either fully or partially as anchoring cavities for anchoring the injected material therein.
A further advantage is that the subject anti-tampering seals are firmly clamped in the cavities housing the molding material which, during the injection molding operation, will fill in any undercuts formed by the clamping nut thread and/or any slots formed in the screw centering blind hole, or the roughness of said anchoring cavities.
A further advantage is that the molding material can comprise any desired plastic materials or low melting metals or metal alloys. By using conventional or recessed nuts, it is moreover possible to reduce the height of the screw threaded portion, to provide a corresponding reduction of the required material amount. Even if small, such a material saving would be very important in a large series making said ball valves.
Yet another advantage is that the injection molding of said filling material is advantageously performed after having fully assembled and possibly tested the valve, thereby the anti-tampering seal also assure a perfectly reliable operation of the valve.
Yet another advantage is that the injection head, or injection molding head, has a simple bush shape and is removably fitted, by a geometrical type of engagement, on the valve locking nut/screw assembly.